Thin film transistor liquid crystal display (TFT-LCD) has become a mainstream flat display device in the market due to its advantages such as small volume, low power consumption and being free of radiation. As a main structure of the TFT-LCD, a liquid crystal panel includes a plurality of pixel units for displaying an image. Each pixel unit includes a TFT for controlling a display function of the pixel unit. In the related art, depending on a material of a channel, the TFTs may be mainly classified into two types, i.e. an oxide semiconductor TFT (oxide TFT for short) and an amorphous silicon (a-Si) TFT. The oxide TFT has a larger on/off current ratio, i.e., in the case that the oxide TFT is turned on, a larger current may be provided and a charging time may be reduced, and in the case that the oxide TFT is turned off, a smaller leakage current may occur and electric leakage may be prevented. Hence, the oxide TFT is more applicable to the manufacture of a high-end display product with a high resolution (high definition) and a high refresh rate (a more smooth dynamic image).
The oxide TFT with a back channel etching (BCE) structure has been widely used due to its advantages such as simple structure, simple manufacture process, small size and small parasitic capacitance. This kind of oxide TFT includes, from bottom to top, a gate electrode, a gate insulation layer, an oxide semiconductor layer, a source electrode and a drain electrode, and a surface of the oxide TFT is covered with a protection layer. The source electrode and the drain electrode are directly lapped onto the oxide semiconductor layer, and a portion of the oxide semiconductor layer located between the source electrode and the drain electrode is a channel region. In the case that the oxide TFT is turned on, the channel region of the oxide semiconductor layer forms a conductive channel of the oxide TFT.
In the case that the source electrode and the drain electrode are directly lapped onto the oxide semiconductor layer, the channel region of the oxide semiconductor layer may be obviously corroded by an etching process for forming the source and drain electrodes. In the related art, in order to overcome this drawback, an additional etching process for forming on the oxide semiconductor layer an etch-stop layer covering the channel region may be provided. In the case that the source and drain electrodes are formed subsequently, the etch-stop layer may be used to prevent the oxide semiconductor layer under the etch-stop layer from being corroded. However, due to this additional etching process, the entire manufacture process may be more complex and the production cost may increase.